Ordinarily, you do not want to go on a deferred prosecution if it is your first DUI charge ever, especially if your BAC reading is under .15. Why? Because the consequences of a sentence for a first DUI, especially if the State will amend the charge to something less serious, could be less onerous than those of a deferred prosecution program.
The main advantages of entering deferred prosecution are that you do not get convicted of the offense, and do not receive penalties. You will however, have to comply with a rigorous treatment program for two years. And the treatment is at your own expense, unless you can get it covered under your insurance or apply for state funding. But you will not have your license suspended if you go on deferred prosecution, nor will you serve jail time.
Disadvantages or risks of deferred prosecution
The disadvantages are that as a condition of being granted deferred prosecution, you must sign a stipulation that if you violate the conditions of the program, and get "revoked," then you will not receive a jury trial or most of the rights that go with it.
Instead, the Court will simply review the police report and make a determination of guilty or not guilty based on that, without live testimony. And, you would not have taken a deferred program, if you thought the evidence against you was weak, you would have gone to trial.
How long does a deferred prosecution program take?
Once you complete your two years of treatment, your are still on probation for five years, and must not commit any similar offenses during that time. If you meet all the requirements, then the charge is dismissed.
In the State of Washington, you can only take a deferred prosecution once in a lifetime.
Final points about deferred prosecution
Do not go on a deferred prosecution unless you acknowledge you have a serious alcohol or substance abuse problem, and are committed to complete abstinence, and completing your treatment faithfully.
If you are more than a first time offender, and you need the treatment, and you follow the requirements, it may be the best thing to happen to you. If you need serious treatment, then it would be part of any sentence if convicted anyway.